SwiftKey is definitely the 3rd-party keyboard of favor here at Android Police (just ask Artem or Cameron), and there's no doubt in our minds that it's worth four bucks. But at two bucks, it's an absolute steal. Today and tomorrow only (November 22nd and 23rd), SwiftKey will be on sale, and that includes the phone version as well as the tablet-optimized edition. That means for the price of one SwiftKey, you can get two! If you haven't already bought it, which I'm guessing a lot of you have.
SwiftKey is well-known for its outstanding prediction engine and customization options, and honestly, I've never used a better 3rd-party keyboard, even if I do still prefer the stock experience, generally speaking.